Another crucial step that needs to be taken before you unwrap is to Apply the objects scale, rotation, and location. It's easy to do, just select the object while in object mode, press "CTRL+A" and click the top option.
Basically, when you create an object, it's centre will be the original position you created it at. When you edit, move, scale, rotate, the object it references all your editing in regard to that origin. So, instead of your finished object being at 0,0,0 on the grid, it might be at 12,255,50. Applying the scale/rotate/locate will set your current position/scale/rotation to 0,0,0.
Hope that helps too
Greenlig
Blender3D - CS3 - VISTA - DBPro